Low-density alloy for golf club head

ABSTRACT

A low-density alloy for a golf club head includes 84 wt %-94 wt % of Ti, 6.5 wt %-9.5 wt % of Al, and/or V less than 1.5 wt %, providing a Ti—Al—V-based alloy having a density smaller than 4.40 g/cm 3 . Trace elements such as Mo, Cr, Fe, Si, and B may be added into the Ti—Al—V-based alloy to provide a titanium alloy having a low density and high elongation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a low-density alloy. More specifically, the present invention relates to a low-density alloy for a golf club head.

2. Description of Related Art

Conventional golf club heads are generally made of stainless steel, such as SUS630 or SUS431 (The U.S. AISI Standard 630 type and 431 type). The process is carried out by a precision dewaxing method in which the density of the material is greater and the strength of the material is lower. However, a thickness of the golf club head must meet the strength requirement. To comply a weight limiting regulation of the golf club head, dimensions of the conventional golf club heads cannot be expanded or enlarged. As a result, the scope of the sweet spot of the ball-hitting face of the golf club head is substantially reduced, leading to an increase in the rate of the ball-hitting failure.

To solve the above problem, titanium alloy has been used to manufacture golf club heads, such as Ti-6Al-4V alloy (6 wt % of Al and 4 wt % of V, with the rest being Ti) disclosed in, e.g., U.S. Pat. Nos. 5,505,795; 5,643,108; 6,832,961; 6,880,222; and 6,905,061. Titanium alloy has a density smaller than that of the stainless steel, and a strength substantially equal to that of the stainless steel, providing better elastic deforming property. Thus, the volume of the golf club head can be increased without increasing the overall weight of the golf club head. As a result, the scope of the sweet spot of the ball-hitting face of the golf club head can be increased, reducing the rate of the ball-hitting failure.

Further, since the titanium alloy has a density smaller than that of the stainless steel, the titanium alloy can be used in some components of the golf club head such as the main body, the striking plate, the cover, and the weight member for adjusting the center of gravity of the golf club head. Further, since the elastic deforming property (elongation) of the titanium alloy is better than that of the stainless steel, a greater elastic deforming effect can be obtained during striking, and the compressive deformation of the ball in contact with the ball-hitting face can be largely reduced. This reduces the loss of striking stress absorbed due to damping. Accordingly, the loss of striking energy is reduced and the hitting performance is improved.

To improve application of the titanium alloy while considering the increase in the volume and the adjustment of the center of gravity of the golf club head, it is necessary to further reduce the density of the titanium alloy while maintaining the mechanical strength.

Other titanium alloys are listed in Table 1.

TABLE 1 Compositions and properties of conventional titanium alloys Patent No. Ti Al Cr Mn V W Ta B Si Nb C Ga F.S(ksi) Y.S(ksi) E % U.S. Pat. No. 5492574 45–46 50–51 4 U.S. Pat. No. 5324367 46 50 2 2–4  0.05–0.2 85–97 62–73 2.6–3.4 EP0549181 46 48 1–3  6–14 72–88 48–74 2.1–1.5 EP0545614 42 46 1–3 1–4 2–6  70–105 55–85 1.6–2   U.S. Pat. No. 5264054 0.5–2 88–96 73–80 1.3–2.1 DE4140707 0.5–2 87–95 69–76 1.2–1.7 DE4140679 0.5–2 88–98 73–83 DE4022403 51–43 46–50 2 1–5 0.1 54–70 2.3–2.6 GB2266315 52–44 46–50 1–3 1–3 FR2695652 48 48 2 2 50–80 EP0405134 48 48 2 2  68–100 50–75 2.2–2.4 GB2266096 48 46 2 2 EP0362470 52–42 46–50 1–3 1–5 U.S. Pat. No. 4902474 52–47 42–46 3–7 120–125  95–100 0.8 U.S. Pat. No. 4923534 50–48 48 2–4 125–150 100–110 0.9 U.S. Pat. No. 4842820 2–4 U.S. Pat. No. 4842817 48 48 4 U.S. Pat. No. 4842819 52–50 46–48 2 U.S. Pat. No. 4857268 49 48 3

OBJECTS OF THE INVENTION

An object of the present invention is to provide a titanium alloy in which the proportion between Al and V in the titanium alloy is adjusted to reduce the density while maintaining the mechanical strength of the titanium alloy, allowing adjustment of the center of gravity and improving the elastic deforming property of the golf club head made of the titanium alloy.

Another object of the present invention is to provide a low-density titanium alloy for a golf club head, wherein the proportion between Al and V in the titanium alloy is adjusted, and trace elements such as Mo, Cr, Fe, Si, and/or B can be selectively added to reduce the density while maintaining the mechanical strength of the titanium alloy, allowing adjustment of the center of gravity and improving the elastic deforming property of the golf club head made of the titanium alloy.

SUMMARY OF THE INVENTION

A low-density alloy for a golf club head in accordance with the present invention comprises 84 wt %-94 wt % of Ti, 6.5 wt %-9.5 wt % of Al, and V less than 1.5 wt %, providing a Ti—Al—V alloy having a density smaller than 4.40 g/cm³. The Ti—Al—V alloy has a low density and high elongation.

Preferably, the Ti—Al—V alloy comprises 8 wt % of Al and 1 wt % of V.

Preferably, the Ti—Al—V alloy further comprises Mo less than 1.2 wt %.

Preferably, the Ti—Al—V alloy further comprises Cr less than 1.2 wt %.

Preferably, the Ti—Al—V alloy further comprises Fe less than 0.6 wt %.

Preferably, the Ti—Al—V alloy further comprises Si less than 0.6 wt %.

Preferably, the Ti—Al—V alloy further comprises B less than 1.0 wt %.

Other objects, advantages and novel features of this invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photomicrograph of a cross section illustrating a low-density alloy for a golf club head in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A first example of a low-density alloy for a golf club head in accordance with the present invention is a Ti—Al—V alloy in which titanium (density 4.51 g/cm³), aluminum (density 2.70 g/cm³), and vanadium (density 5.79 g/cm³) are the main compositions (See Table 2).

Turning now to FIG. 1, a photomicrograph of a cross section of the low-density alloy for the golf club head in accordance with a preferred embodiment of the present invention is illustrated.

The Ti—Al—V alloy (or simply titanium alloy) comprises 84 wt %-94 wt % of Ti, 6.5 wt %-9.5 wt % of Al, and V less than 1.5 wt %. The titanium alloy has a density smaller than 4.40 g/cm³. Preferably, the titanium alloy comprises 91 wt % of Ti, 8 wt % of Al, and 1 wt % of V (Ti-8Al-1V, see Table 2).

As compared to the conventional Ti-6Al-4V alloy, the density of the titanium alloy in accordance with the present invention is reduced and the toughness of the titanium alloy in accordance with the present invention is improved by increasing the amount of aluminum, thereby obtaining the required low-density property. Further, by reducing the amount of vanadium, the flowability and the auxiliary degassing effect during casting are improved without adversely affecting the mechanical properties of the titanium alloy. The Ti—Al—V alloy in accordance with the present invention can be used to manufacture component(s) of a golf club head, such as a main body, a striking plate, a cover, and/or a weight member, preferably the striking plate.

Since the density (4.40-4.34 g/cm³) of the Ti-8Al-1V alloy in accordance with the present invention is lower than that (4.42 g/cm³) of the conventional Ti-6Al-4V alloy, the Ti-8Al-1V alloy in accordance with the present invention can be used in the components of the golf club head to reduce the overall weight of the golf club head without adversely affecting the mechanical properties. As a result, the center of gravity of the golf club head can be adjusted.

Table 2 shows the second, third, fourth, and fifth examples of the low-density alloy in accordance with the present invention, in which trace elements (such as Mo less 1.2 wt %, Cr less than 1.2 wt %, Fe less than 0.6 wt %, Si less than 0.6%, and B less than 1.0 wt %) are selectively added into the Ti-8Al-1V alloy.

By adding an appropriate amount of molybdenum (Mo), uniformly distributed carbonide can be precipitated from the alloy and the heat-resisting property is improved, reducing heat crack during welding of the alloy, improving the hardening property, and improving the strength at high temperature. By adding an appropriate amount of chromium (Cr), the rust-resisting property is improved and the life of the golf club head is prolonged. By adding an appropriate amount of iron (Fe), the alloy has improved plasticity for processing. By adding an appropriate amount of silicon (Si), the flowability of the molten metal is improved. By adding an appropriate amount of boron (B), the structure of the alloy is stable at high temperature, providing improved anti-oxidation property, improved toughness, and improved plasticity, thereby improving the mechanical properties of the alloy.

In the alloy of the second example 0.25 wt %-0.5 wt % of Mo is added, in the alloy of the third example 0.4 wt %-0.6 wt % of Cr is added, in the alloy of the fourth example 0.2 wt %-0.4 wt % of Fe is added, and in the alloy of the fifth example 0.25 wt %-0.35 wt % of Si is added. In addition, B less than 1.0 wt % can be added into the alloy in accordance with the present invention for forming a golf club head. The Ti—Al—V alloys in the second through fifth examples of the present invention can be used to manufacture component(s) of a golf club head, such as the main body, striking plate, cover, and weight member, preferably the striking plate.

The golf club head manufactured with the above five examples of Ti—Al—V-based alloy added with trace elements such as Mo, Cr, Fe, Si, and/or B has a density smaller than that of Ti-6Al-4V alloy, and has an elongation higher than that of Ti-6Al-4V alloy. The elongation E % (elastic deforming property) of the low-density Ti—Al—V alloy in accordance with the present invention is increased within the elastic limit of the material. This improved elastic deforming property allows greater elastic deforming extent during striking, thereby improving the hitting performance. Further, use of the low-density Ti-8Al-1V alloy allows reduction in the overall weight of the golf club head. Further, using the low-density Ti-8Al-1V alloy to manufacture component(s) (such as the main body, cover, striking plate, and/or weight member) of the golf club head allows adjustment of the center of gravity of the golf club head. As a result, the volume of the golf club head can be maximized without increasing the weight of the golf club head. The scope of the sweet spot of the golf club head is increased and the rate of the ball-hitting failure is reduced. Further, the design flexibility of the golf club head is increased.

TABLE 2 Compositions and properties of different titanium alloys tensile 0.2% yield strength strength elongation hardness density alloy (ksi) (ksi) (%) (HRC) (g/cm³) Ti—6Al—4V 120–140 110–130 3–5 32–35 4.42 Ti—8Al—1V 110–118  99–100 8–9 28–31 4.34–4.40 Ti—8Al—1V—0.25—0.50Mo 122–127 111–112 7 34–35 4.34–4.35 Ti—8Al—1V—0.4—0.60Cr 128–129 109–114 6–7 33–34 4.34–4.35 Ti—8Al—1V—0.20—0.40Fe 120–123 104–115 7–8 33–34 4.37 Ti—8Al—1V—0.25—0.35Si 122–135 114–129 6–8 31–33 4.32

TABLE 3 Alloying elements of titanium alloys of Ti—6Al—4V and Ti—7.5Al—0.05V—0.02Si—0.06B₄C (present invention) alloy Al (wt %) V (wt %) Si (wt %) B₄C (wt %) Fe (wt %) C (wt %) N (wt %) O (wt %) Ti—6Al—4V  5.5–6.75 3.5–4.5 <0.1 — <0.3 <0.1 <0.05 <0.2 Ti—7.5Al—0.05V—0.02Si—0.06B₄C 7.2–7.8 0.02–0.06 0.22 0.06 0.06 0.04 0.01 0.21

TABLE 4 Comparison of titanium alloys of Ti—6Al—4V and Ti—7.5Al—0.05V—0.02Si—0.06B₄C (present invention) in cannon test thickness of alloy Sample striking plate hits Ti—6Al—4V 1 3.1 mm 2,348 Ti—7.5Al—0.05V—0.02Si—0.06B₄C 1 3.1 mm 3,000 2 3,000 3 3,000 4 3,000

As given in Tables 3 and 4, a sixth example of the low-density alloy in accordance with the present invention is illustrated. In comparison with the first to fifth examples, the low-density alloy of Ti-7.5Al-0.05V-0.02Si-0.06B₄C comprises 7.2 wt %-7.8 wt % of Al, 0.02 wt %-0.06 wt % of V, 0.22 wt % of Si, 0.06 wt % of B₄C, 0.06 wt % of Fe, 0.04 wt % of C, 0.01 wt % of N, 0.21 wt % of O and the balance is essentially Ti. The mechanical properties of Ti-7.5Al-0.05V-0.02Si-0.06B₄C are similar to those of Ti-6Al-4V, but the density of Ti-7.5Al-0.05V-0.02Si-0.06B₄C is 4.32 g/cm³ is less than Ti-6Al-4V (4.42 g/cm³). In cannon testing, a striking plate made from Ti-7.5Al-0.05V-0.02Si-0.06B₄C of the present invention has passed the 3,000-hit test. Accordingly, the club head members made from Ti-7.5Al-0.05V-0.02Si-0.06B₄C can further reduce the weight of the golf club head, and lower a specific center of gravity of the golf club head. Other golf club head members suitable for reducing weight are club head body, crown plate, striking plate and club weight member.

While the principles of this invention have been disclosed in connection with specific embodiments, it should be understood by those skilled in the art that these descriptions are not intended to limit the scope of the invention, and that any modification and variation without departing the spirit of the invention is intended to be covered by the scope of this invention defined only by the appended claims. 

1. A low-density alloy for a golf club head, comprising 84 wt %-94 wt % of Ti, 6.5 wt %-9.5 wt % of Al, and V less than 1.5 wt %, providing a Ti—Al—V alloy having a density smaller than 4.40 g/cm³.
 2. The low-density alloy for a golf club head as claimed in claim 1 wherein the Ti—Al—V alloy comprises 8 wt % of Al and 1 wt % of V.
 3. The low-density alloy for a golf club head as claimed in claim 1 wherein the Ti—Al—V alloy further comprises Mo less than 1.2 wt %.
 4. The low-density alloy for a golf club head as claimed in claim 1 wherein the Ti—Al—V alloy further comprises Cr less than 1.2 wt %.
 5. The low-density alloy for a golf club head as claimed in claim 1 wherein the Ti—Al—V alloy further comprises Fe less than 0.6 wt %.
 6. The low-density alloy for a golf club head as claimed in claim 1 wherein the Ti—Al—V alloy further comprises Si less than 0.6 wt %.
 7. The low-density alloy for a golf club head as claimed in claim 1 wherein the Ti—Al—V alloy further comprises B less than 1.0 wt %.
 8. The low-density alloy for a golf club head as claimed in claim 1 wherein the Ti—Al—V alloy comprises 7.2 wt %-7.8 wt % of Al and 0.02 wt %-0.06 wt % of V.
 9. The low-density alloy for a golf club head as claimed in claim 1 wherein the Ti—Al—V alloy further comprises 0.06 wt % of B₄C. 